Friday, January 30, 2015

I was sick, but I couldn't resist the temptation to image part of the flyby of asteroid 2004 BL86 the other night. Below is a time-lapse video taken of the event as the asteroid moved across Messier 44, the Beehive Cluster. Of course, both objects are VERY far apart. The asteroid was about 4 light seconds away (approximately 3.1 times the distance between Earth and the Moon), while M44 is around 577 light years away.

The video compresses about 27 minutes down to 6 seconds.

Each frame is a 20-second exposure taken at ISO-3200 with a Canon EOS Rebel T3. I did not use autoguiding, so there is some visible periodic error. Passing clouds cause the brightening and dimming of the background.

This is the first set of images taken with the Takahashi Epsilon 200 since I cleaned the mirror. The collimation is still a little off, but I didn't have time and energy that night to fine tune it. I'm looking forward to getting the scope back into full service soon!

The SHSU observatory is the proud owner of a rare gem: a Takahashi Epsilon 200 astrograph. It is a fast (f/4) Newtonian telescope with a hyperbolic primary mirror and a dedicated field-flattener lens. It was designed specifically for astroimaging. Dr. Anjal Sharma, with the help of Mike Prokosch, Brian Neitfeld, myself, and others worked to restore the telescope and its mount to operational condition and to establish procedures for producing images. Anjal documented the restoration in Resurrecting an Old Classic. The Epsilon 200 has not been manufactured for about 20 years now, and according to Anjal there are probably only about three dozen of them in existence worldwide. Maintaining and using this exciting piece of equipment has been a pleasure and a privilege, and I hope that it will be of benefit to SHSU and its students in the future.

Anjal had to focus his energies elsewhere, and so left me more-or-less in charge of the scope and its care. However,I haven't been able to make trips to the observatory as frequently as I did before my youngest was born. As a result, the Epsilon 200 has not had much use, and it has not been maintained as well as it should. It's a great scope and is capable of capturing some beautiful images, so I'm slowly trying to bring it back up to a presentable and operational state. I reread Anjal's account of the restoration and a few Takahashi manuals (for similar scopes), and decided to tackle cleaning the mirror.

The mirror was a mess. Dirt, smoke, dust, mold, spiders, various other fauna and a strange green fibrous substance have slowly built up gunk on the mirror over the years. Below is a photo of the mirror in its cell. Note the cobwebs. There were several spots of mold and something else that I can only describe as a "biological byproduct." The mirror is held in place by six clips. In addition, six small compression washers hold the sides of the mirror down inside the cell. It's in there pretty snugly.

Here is the mirror removed from the cell. Working on this telescope has made me appreciate even more the quality of workmanship that Takahashi puts into their products. This is a serious telescope that was meant to be used for serious work.

I placed the mirror into a plastic tub filled with distilled water and dish soap. Distilled water should be used because tap water and bottled drinking water contain minerals that can leave deposits. After letting it soak for an hour, I very carefully cleaned the surface with cotton balls. (The trick with the cotton balls is to move them from the inside out and to not put any pressure other than their own weight on the mirror surface.)

After three passes with the cotton balls, I rinsed the mirror with more distilled water and let it air dry. Below is the result. There are a few specs of dust that landed while it was drying, and a few spots that did not come clean. These are optically insignificant.

I also cleaned dust and cobwebs out of the tube, collimated the scope, and realigned the finders and the guide scope. Here is the reassembled scope.

I wish I had remembered to bring a DSLR, but here is a photo of some birds sitting on a power line about a quarter of a mile away, taken afocally with my phone through one of the few eye pieces that will come to focus on this scope.

I'm not an expert on telescope mirrors, but this mirror looked practically brand new after its cleaning. I'm convinced that it will continue to serve up beautiful images for many more years.

There is still more work to do: fine-tuning the collimation, cleaning up the mount, and cleaning out the shed. In addition, I am going to write up an operations manual for students and faculty who want to use the scope for research.

A follow-up report on the astrograph:

After reassembling everything, the scope sat for quite a while before I had the chance to go out and collimate it. I struggled and fought with the adjustment screws, but could never get it quite right. This was not unusual, though, as we've never gotten the mirrors aligned properly.

We took it to Land, Sea, & Sky, Takahashi's authorized distributor in the Americas, for alignment and further cleaning. Fred Garcia, the Tak expert, reported that the primary mirror was not installed correctly! Well, color me Takahashi yellow! I'm guessing that the mirror was misaligned even before Anjal rebuilt the scope, because he marked the mirror position before cleaning it years ago. That would explain why we've NEVER been able to get it properly aligned.

As of this update (June 2016) I haven't had time to do any imaging on the Epsilon-200 since it was fixed. However, the university has been putting it to good use observing exoplanet transits!

Monday, January 19, 2015

I took the clutch assembly and RA motor dust cover apart and found that the gear on the RA motor had simply come loose. I reattached it and now it is working fine, assuming I got the gear spacing correct.

Sunday, January 18, 2015

I was taking pictures of C/2014 Q2 Lovejoy the other night when the mount stopped tracking. I assumed that the batteries were dead, but the power light was still its normal brightness. It has always gotten dimmer when the batteries finally run out of juice.

I put in a fresh set of batteries and went out tonight to try imaging the comet, only to find that the clutch is apparently not engaging with the RA motor.

So, I guess I'll be out of the astrophotography gig for a while, except on the rare occasions that I can make it out to the observatory. I've been thinking about buying a new mount, anyway, but that may be much later than sooner. In the meantime I am going to take a stab at fixing this one. Wish me luck(y stars)!

Sunday, January 11, 2015

I finally got a break in the weather on January 7 where I could go out and image C/2014 Q2 Lovejoy. Even in the 91% illumination of the waning Moon, the comet was still visible to the naked eye in the constellation Eridanus. While not as visually interesting as, say, C/2011 L4 PANSTARRS, I think it is the prettiest comet that I've imaged so far. Other amateur photographers have made some stunningimages. Here is mine, made with my modest setup:

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About Me

I am an amateur astronomer living on the edge of the Piney Woods near Huntsville, TX. In addition to my own modest telescopes, I have access to a Takahashi Epsilon-200 that I regularly use for imaging. Most of the images on this blog were taken using either a Canon EOS Rebel XS (1000D) or T3 (1100D) DSLR mounted on the Epsilon-200, but I also image using an inexpensive Orion ShortTube 80 on a Vixen Super Polaris mount.